[Purification and properties of levansucrase of Gluconobacter oxydans L-1].

Levansucrase of G. oxydans L-1 which catalyzes the synthesis of the polysaccharide levan from the fructofuranosyl residues of sucrose has been isolated from the culture fluid and purified by chromatography on hydroxyapatite and gel-filtration on Sephadex G-100. The molecular weight of levansucrase as measured by DS-Na polyacrylamide gel electrophoresis is about 58000. The enzyme contains 25.86% of acidic amino acids, 13.74% of basic amino acids and 12.77% of aromatic amino acids. No cystine or cysteine residues were detected in the acid hydrolysate. The UV-absorption spectrum of the purified protein has a maximum at 280 nm and a minimum at 254 nm. The kinetic data suggest that levansucrase catalyzes levan formation, sucrose hydrolysis and sucrose glycosyl-free glucose exchange reactions. The initial rates of liberation of labelled glucose and labelled fructose during transfructosylation have been determined. Low molecular weight levans accelerate the rate of the polysaccharide formation and increase the ratio of the formed levan to free fructose.